I recently purchased the Alphabet Drills book by Nancy Gyes and it has totally changed my life. Well, not quite; it has revolutionized our training sessions.
The book is simply beautiful and the drawings are pretty easy to understand. I do spend a lot of time thinking, "No way can we do that!" Turns out we can, the the exercises are pretty much broken down from easy to complex.
We started working on the letter T which was covered in our class a couple of months ago. It was nice to be challenged by a few complex additions to the easy exercise.
All the students in our Agility class purchased this book, which our instructor totally appreciates. She just emails us the letter of the week and we all come prepared and know what to expect in class. This week we are working on the letter M.
I totally love this book and I see myself using it for quite a long time.
It also comes with a CD that includes a trial of Clean Run Course Designer.